化工厂遗留地铬污染土壤化学淋洗修复研究
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国家自然科学基金项目(41171251,41471255)资助


Effect of chemical leaching remedying chromium contaminated soil in deserted chemical piant site
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    摘要:

    选取了济南市某铬渣堆放场地表土壤为实验目标,采用振荡淋洗法研究了水、EDTA、柠檬酸、盐酸、CaCl2、NaOH和磷酸等淋洗剂对铬污染场地铬污染物的淋洗效果,并从中筛选出最佳淋洗剂,探讨了淋洗剂浓度、土液质量比、振荡淋洗时间、淋洗液pH等对淋洗条件的影响。结果显示,选取的土壤样品均超过国家土壤标准,钛白生产车间土样污染程度最轻,北部厂区污染最重,最高铬污染物含量达到7 149 mg kg-1;土壤活性指数I显示,万吨铬盐生产车间土壤的活性指数最高达到0.291 8,铬盐生产车间活性指数最低;水、盐酸、柠檬酸、CaCl2、NaOH、磷酸等对总铬的去除率比较低,EDTA的淋洗效果最佳;EDTA的最佳淋洗浓度为0.1 mol L-1;最适土液质量比为1:10;最适振荡淋洗时间为1 h;最适淋洗液pH 为5;所有淋洗试验最高去除率为pH 10时,北部厂区样品在0.1 mol L-1EDTA淋洗液,土液质量比为1:10,振荡淋洗时间1 h取得,总铬的去除率可达到22%,Cr6+去除率可达到98.5%。

    Abstract:

    Chromium and its salts are widely used in alloys, electroplating, leather, dyes, printing and dyeing, catalysis, medicine and other industries as an important industrial raw material. Therefore, there is a serious chromium contamination problem in many legacy chemical plants , making it difficult to re-use. Chromium contaminated site remediation problem of the industrial wastelands is imminent. Currently, the repair of chromium contaminated sites are mainly chemical leaching repair technology, electrochemical remediation, bioremediation, chemical fixation, and chemical reduction methods. The surface soil was selected from a deserted chemical plant in Jinan as the experiment samples, including the following five samples, the titanium white workshop sample, chromic salt workshop sample, the ten thousand ton chromic salt workshop, the east chromium slag dump site sample and the north section of the plant sample. Chemical oscillation leaching experiments was used to repair the contaminated soil samples. The vast majority of Cr (Ⅵ) was removed from the soil samples by using the eluent. The majority of the use of chemical eluent Cr (Ⅵ) is removed from the soil. While the Cr (Ⅲ) was stable in soil, part of Cr (Ⅲ) was displaced, the chromium contaminated soil at the site get repaired in some degree to provide the basis for the chemical plants chromium chemical remediation of contaminated soil. Laboratory simulation tests were conducted to examine effects of different leaching reagents(water, 0.1 mol L-1 EDTA, 0.1 mol L-1 CTA, 0.1 mol L-1 HCl,0.1 mol L-1 CaCl2,0.1 mol L-1 NaOH and 0.1 mol L-1H3PO4) extracting Cr from the soils sampled from the plant with a view to screening out one that is the most effective in remedying Cr contaminated soil. By measuring total chromium and Cr (Ⅵ) of the filtrate, the best eluent was selected from the eluents we have chose by leaching experiment. According to the selected best eluent, we explored the conditions of eluent concentration, soil liquid mass ratio, oscillation time, the eluent pH on leaching effect. Setting the eluent concentration gradient, 0.005, 0.01, 0.02, 0.05, 0.1, 0.15 mol L-1, different soil liquid mass ratio, 1: 2, 1:5, 1: 10, 1: 15, 1: 20,different oscillation time, 0.5, 1, 2, 4, 8 h, the eluent pH ,4.5, 5, 6, 7, 8, 9, 10, we found the leaching removal different under the different conditions. We proposed “I”, the chromium contaminated soil activity index, to indicate the proportion of Cr (Ⅵ) in total chromium of the soil sample. The results showed that all the soil samples exceeded the national standard for soil environment in Cr contamination; the soil samples from the Titanium white production workshop were the lowest in pollution degree, while those from the north section of the plant were the highest, reaching as high as 7 149 mg kg -1; in terms of soil activity index “I”,the soil samples from the ten thousand ton chromic salt workshop were the highest, reaching up to 0.291 8, whereas those from the ordinary chromic salt workshop the lowest; the reagents, Water, HCl, CTA,CaCl2, NaOH and H3PO4, were all quite low in total chromium removal rate; EDTA was the most effective one, when it was 0.1 mol L-1 in concentration, 1:10 in soil liquid mass ratio and 5 in pH for 1 h of leaching oscillation. On the whole, the removal of Cr (Ⅵ) was low, the removal of Cr (Ⅵ) was ideal. In treating the soil samples from the north section of the plant, its total Cr removal rate reached as high as 22% and Cr6+ removal rate 98.5%. With the continuous optimization of elution conditions, oscillation leaching removal is constantly improved . But the chromium content is still more than the national standard after soil leaching process, we need further processing of contaminated soil. we can consider adding an oxidant to activate the chromium ions, promoting the activity of migration ,then improve the leaching removal.

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李世业,成杰民.化工厂遗留地铬污染土壤化学淋洗修复研究[J].土壤学报,2015,52(4):869-878. DOI:10.11766/trxb201410080507 Li Shiye, Cheng Jiemin. Effect of chemical leaching remedying chromium contaminated soil in deserted chemical piant site[J]. Acta Pedologica Sinica,2015,52(4):869-878.

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  • 收稿日期:2014-10-08
  • 最后修改日期:2015-03-11
  • 录用日期:2015-04-10
  • 在线发布日期: 2015-04-24
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